For everyone who’s ever said, “I’m no good with numbers,” here’s a practical, user-friendly field guide to the math you really need.

Your dinner bill came to $78.35, plus tip, divided amongst you and two friends. So how did you end up paying $50? In life, there are plenty of instances where a quick calculation would come in handy. Contrary to popular belief, the ability to calculate a tip, eyeball square area, or convert kilometers to miles—without using your fingers or moving your lips—is not inborn. Everyday math skills can be painlessly learned and easily mastered, transforming you from a person who doesn’t know the meaning of APR into someone who understands credit card rates and their long-term impact on your wallet. Broken into sections which review basic arithmetic from fractions to percents, provide situational problems from cooking to gambling, and demystify terms from statistics to relative magnitude to probability, this is the one guide that anyone who took “Math for English majors” can’t live without.